High frequency switching component

ABSTRACT

A high frequency switching component for being connected to a transmission circuit, a reception circuit, and an antenna to be used for switching to either a state in which the transmission circuit is connected to the antenna, or a state in which the reception circuit is connected to the antenna, comprising: a multilayer circuit board, on which there is formed a circuit including: a transmission circuit terminal to be connected to the transmission circuit; a reception circuit terminal to be connected to the reception circuit; an antenna terminal to be connected to be the antenna; a ground terminal; a first diode whose anode is connected to the transmission circuit terminal and the cathode thereof is connected to the antenna terminal; a second diode whose anode is connected to the reception circuit terminal and the cathode thereof is connected to the ground terminal; a signal line for connecting the transmission circuit terminal, the reception circuit terminal, and the antenna terminal via the first diode; and an inductor or an LC filter disposed between the signal line and the ground terminal to reduce noise on the signal line; in which the transmission circuit terminal, the reception circuit terminal, the antenna terminal, the ground terminal, the first diode, and the second diode are disposed on a surface of the multilayer circuit board; at least a part of the signal line being disposed inside the multilayer circuit board; and the inductor being disposed either inside or on the surface of the multilayer circuit board.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to high frequency switching components,and more particularly, the invention relates to high frequency switchingcomponents formed by using a multilayer circuit board so as to preventnoise.

2. Related Art

In digital portable phones, high frequency switches are connected totransmission circuits, reception circuits, and antennas to be used forswitching connections between the transmission circuits and theantennas, and connections between the reception circuits and theantennas.

For example, Japanese Unexamined Patent Application Publication No.7-202502 provides a high frequency switching component comprising such ahigh frequency switch, which is of keen interest to the background ofthe present invention.

The high frequency switching component is formed by using a multilayercircuit board. Circuit elements forming a high frequency switch aredisposed in the multilayer circuit board and on a surface thereof, bywhich miniaturization of the high frequency switching component isachieved. With this arrangement, an area necessary to mount the highfrequency switching component can be reduced.

In a high frequency circuit incorporating such a high frequency switch,it is essential to take measures for reducing noise, includingelectrostatic surges, that is, surge currents which occur when built-upstatic electricity is discharged.

In order to prevent such noise, conventionally, a separatenoise-preventing component has been mounted on an appropriate wiringboard with the high frequency switching component.

However, in such an arrangement, it is necessary to allocate an area formounting the noise-preventing component on the wiring board. As aresult, this arrangement is a hindrance to the miniaturization of thewiring board. In addition, since the noise-preventing component isrequired to be a discrete component, this causes an increase in cost.

As another conventional noise-preventing measure, a resin coating isapplied on an antenna to prevent an electrostatic current surge fromentering the antenna.

However, the resin coating can come off due to deterioration of theresin. Under such circumstances, an electrostatic surge can cause greatdamage to the high-frequency switch, or to an external circuit connectedto the antenna or the high-frequency switch, and can lead even to thedestruction of the external circuit.

As noise-preventing components, varistors and Zener diodes are known.When a varistor or a Zener diode is used as a component for preventingelectrostatic surges, the capacitance between terminals must beincreased. Thus, these components cannot be used in a signal line, andaccordingly cannot be used for preventing electrostatic surges in a highfrequency circuit incorporating such a high frequency switch.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a highfrequency switching component capable of solving the above-describedproblems.

One embodiment of the present invention provides a high frequencyswitching component for being connected to a transmission circuit, areception circuit, and an antenna and having two states, a state inwhich the transmission circuit is connected to the antenna, and a statein which the reception circuit is connected to the antenna. In addition,the high frequency switching component has a multilayer circuit board.

Linked to the multilayer circuit board, there is formed a circuit usedfor a high frequency switch including a transmission circuit terminal tobe connected to a transmission circuit, a reception circuit terminal tobe connected to the reception circuit, an antenna terminal to beconnected to be the antenna, a ground terminal, a first diode whoseanode is connected to the transmission circuit terminal and whosecathode is connected to the antenna terminal, a second diode whose anodeis connected to the reception circuit terminal and whose cathode isconnected to the ground terminal, and a signal line for connecting thetransmission circuit terminal, the reception circuit terminal, and theantenna terminal via the first diode.

In addition, the transmission circuit terminal, the reception circuitterminal, the antenna terminal, the ground terminal, the first diode,and the second diode are disposed on a surface of the multilayer circuitboard. Furthermore, at least a part of the single line is disposedinside the multilayer circuit board.

In such a high frequency switching component, in order to solve theabove-described technological problems, the present invention provides astructure in which an inductor is disposed between the signal line andthe ground terminal to eliminate noise within or on the surface of themultilayer circuit board.

The above inductor is preferably provided by a line electrode disposedinside the multilayer circuit board.

In addition, in this embodiment of the present invention, particularly,it is preferable that the inductor is disposed between the groundterminal and a part at which the signal line is connected to the antennaterminal.

Further, in such a high frequency switching component, anotherembodiment of the present invention provides a structure in which an LCfilter is disposed on the signal line to eliminate noise, and the LCfilter is arranged inside or on the surface of the multilayer circuitboard.

The above LC filter is preferably disposed inside the multilayer circuitboard.

In addition, in this embodiment of the present invention, particularly,it is preferable that the LC filter is disposed at a part at which thesignal line is connected to the antenna terminal.

Other features and advantages of the present invention will becomeapparent from the following description of the invention which refers tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the circuit diagram of a circuit structure arranged in a highfrequency switching component 1 according to a first embodiment of thepresent invention.

FIG. 2 is a perspective view showing the appearance of the highfrequency switching component 1 having the circuit structure shown inFIG. 1.

FIG. 3 is an exploded perspective view of the multilayer circuit board 2shown in FIG. 2.

FIG. 4 is a circuit diagram showing a circuit structure arranged in ahigh frequency switching component 101 according to a second embodimentof the present invention.

FIG. 5 is a perspective view showing the appearance of the highfrequency switching component 101 having the circuit structure shown inFIG. 4.

FIG. 6 is an exploded perspective view of a multilayer circuit board 102shown in FIG. 5.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

FIGS. 1 and 3 illustrate a high frequency switching component 1according to a first embodiment of the present invention.

First, referring to FIG. 1, a description will be given of the structureof a circuit disposed in the high frequency switching component 1.

The high frequency switching component 1 includes a transmission circuitterminal Tx for being connected to a transmission circuit, a receptioncircuit terminal Rx for being connected to a reception circuit, anantenna terminal ANT for being connected to an antenna, and a groundterminal GND. In addition, the high frequency switching component 1includes a first control terminal T1 and a second control terminal T2.

The transmission circuit terminal Tx is connected to the anode of afirst diode D1 via a first capacitor C1. The cathode of the first diodeD1 is connected to the antenna terminal ANT via a second capacitor C2.The anode of the first diode D1 is connected to a ground terminal GND,that is, the anode is grounded, via a series circuit constituted of afirst transmission line SL1 and a third capacitor C3. In addition, thefirst control terminal T1 is connected to an intermediate point betweenthe first transmission line SL1 and the third capacitor C3, and a firstcontrol circuit for switching the high frequency switching component 1is to be connected to the first control terminal T1.

The second capacitor C2 connected to the antenna terminal ANT isconnected to the reception circuit terminal Rx via a series circuitconstituted of a second transmission line SL2 and a fourth capacitor C4.In addition, the anode of a second m diode D2 is connected to theintermediate point between the second transmission line SL2 and thefourth capacitor C4. The cathode of the second diode D2 is connected toa ground terminal GND via a fifth capacitor C5, that is, the cathodethereof is grounded. The second control terminal T2 is connected to theintermediate point between the second diode D2 and the fifth capacitorC5 via a resistor R. A second control circuit for switching the highfrequency switching component 1 is to be connected to the second controlterminal T2.

In such a high frequency switching component 1, in order to connect thetransmission circuit and the antenna in order to perform transmission, apositive voltage is applied to the first control terminal T1 by thefirst control circuit, which is not shown in the figure. With thisapplied voltage, both the first and second diodes D1 and D2 are switchedon. In this situation, the DC voltage applied to the first controlterminal T1 is applied only to a circuit including the first and seconddiodes D1 and D2, and the voltage is blocked by the first to fifthcapacitors C1 to C5.

As described above, when the first and second diodes D1 and D2 areswitched on, a signal applied to the transmission circuit terminal Tx bythe transmission circuit is transmitted to the antenna via the antennaterminal ANT. In addition, the signal from the transmission circuit isnot transmitted to the reception circuit terminal Rx, since the secondtransmission line SL2 is placed in a resonant condition by beinggrounded via the second diode D2, and as a result, an extremely largeimpedance is observed in the direction of the reception circuit terminalRx from a node A.

On the other hand, in the high frequency switching component 1, in orderto connect the reception circuit and the antenna to perform reception,no voltage is applied to the first control terminal T1, and a positivevoltage is applied to the second control terminal T2. With this appliedvoltage, both the first and second diodes D1 and D2 are switched off. Asa result, a signal received from the antenna via the antenna terminalANT is transmitted to the reception circuit via the reception circuitterminal Rx, and is not transmitted to the transmission circuit via thetransmission circuit terminal Tx.

In this way, with the high frequency switching component 1, controlvoltages are applied to the first and second control terminals T1 and T2so as to switch to a state in which the transmission circuit isconnected to the antenna and a state in which the reception circuit isconnected to the antenna.

In this embodiment, the high frequency switching component 1 describedabove also includes the first to third inductors L1 to L3. The inductorsL1 to L3 are disposed respectively between the ground terminal GND andthe antenna terminal ANT, the transmission circuit terminal Tx, and thereception circuit terminal Rx. With this arrangement, the inductors L1to L3 serve to eliminate noise such as electrostatic surges occurring onthe signal line 3. More specifically, the first inductor L1 is disposedbetween the part at which the signal line 3 is connected to the antennaterminal ANT and the ground terminal GND. The second inductor L2 isdisposed between the part at which the signal line 3 is connected to thetransmission circuit terminal Tx and the ground terminal GND. The thirdinductor L3 is disposed between the part at which the signal line 3 isconnected to the reception circuit terminal Rx and the ground terminalGND.

With the first to third inductors L1 to L3, when a noise component isgenerated in a signal running through the signal line 3, the noisecomponent flows through one of the inductors L1 to L3 to the groundterminal GND, with the result that the noise component can beeliminated. Particularly, the first inductor L1 disposed near theantenna terminal ANT effectively allows an electrostatic surge thatenters from the antenna to flow to the ground terminal GND, and servesto prevent the electrostatic surge from entering either the highfrequency switching component 1 or an external circuit connected to theswitching component. As a result, the first inductor L1 prevents damageboth to the high frequency switching component 1 and to externalcircuits.

Furthermore, by appropriately selecting the inductance value of each ofthe first to third inductors L1 to L3, the inductors L1 to L3 areadapted to be suitable for prevention of electrostatic surges, and forthe prevention of noise on the low-frequency side, between directcircuit and a signal frequency. In addition, the inductors L1 to L3 canhave the additional function of performing matching adjustments in thehigh frequency switching component 1.

FIG. 2 is a perspective view illustrating the appearance of the highfrequency switching component 1 comprising the circuit shown in FIG. 1.FIG. 3 is an exploded perspective view of a multilayer circuit board 2disposed in the high frequency switching component 1 shown in FIG. 2. InFIGS. 2 and 3, the same reference numerals are given to parts equivalentto those shown in FIG. 1 so that the linkages between FIGS. 1, 2, and 3can be easily understood.

The multilayer circuit board 2 disposed in the high frequency switchingcomponent 1, as shown in FIG. 3, is formed by laminating a plurality ofinsulation layers 4 to 10. The insulation layers 4 to 10 are formed of adielectric material.

Referring to FIG. 3, the description of the circuit board 2 will startfrom the insulation layer 4 at the bottom. Over almost the entire firstinsulation layer 4, a ground electrode 11 is formed. The groundelectrode 11 is connected to the ground terminal GND shown in FIG. 2.

On a second insulation layer 5, first to third inductors L1 to L3 areformed by line electrodes. These line electrodes for forming the firstto third inductors L1 to L3 provide microstrip line structures with theground electrode 11.

An end of each of the line electrodes forming the first to thirdinductors L1 to L3 is connected to the ground electrode 11 via arespective one of via-holes 12, 13, and 14. The other end of the lineelectrode forming the first inductor L1 is connected to the antennaterminal ANT shown in FIG. 2. The other end of the line electrodeforming the second inductor L2 is connected to the transmission circuitterminal Tx shown in FIG. 2. The other end of the line electrode formingthe third inductor L3 is connected to the reception circuit terminal Rxshown in FIG. 2.

On a third insulation layer 6, a capacitor electrode 15 used for a thirdcapacitor C3 is formed. The other capacitor electrode used for the thirdcapacitor C3 is provided by the ground electrode 11.

On a fourth insulation layer 7, line electrodes used for first andsecond transmission lines SL1 and SL2 are formed. These first and secondtransmission lines SL1 and SL2 comprise microstrip line structuresformed by these line electrodes and the ground electrode 11. An end ofthe first transmission line SL1 is connected to a capacitor electrode 15used for the third capacitor C3 through a via-hole 16.

On a fifth insulation layer 8, capacitor electrodes 17, 18, and 19 usedfor the first, second, and fourth capacitors C1, C2, and C4 are formed.The capacitor electrode 17 used for the first capacitor C1 is connectedto the second inductor L2 by a via-hole 20. The capacitor electrode 18used for the second capacitor C2 is connected to the first inductor L1by a via-hole 21. The capacitor electrode 19 used for the fourthcapacitor C4 is connected to the third inductor L3 by a via-hole 22.

On a sixth insulation layer 9, the other capacitor electrodes 23, 24,and 25 used for the first, second, and fourth capacitors C1, C2, and C4are formed. These capacitor electrodes 23, 24, and 25 oppose thecapacitor electrodes 17, 18, and 19 through the insulation layer 9.

The capacitor electrode 23 used for the first capacitor C1 is connectedto the first transmission line SL1 by a via-hole 26. The capacitorelectrode 24 used for the second capacitor C2 is connected to one end ofthe second transmission line SL2 by a via-hole 27. The capacitorelectrode 25 used for the fourth capacitor C4 is connected to the otherend of the second transmission line SL2 by a via-hole 28.

On a seventh insulation layer 10 at the top are formed conductive lands29, 30, 31, 32, 33, 34, and 35.

The conductive land 29 is connected to the first control terminal T1shown in FIG. 2, and is also connected to the first transmission lineSL1 and the capacitor electrode 15 used for the third capacitor C3through the via-hole 16.

The conductive land 30 is connected to the second control terminal T2shown in FIG. 2.

The conductive land 31 is connected to the capacitor electrode 24 usedfor the second capacitor C2 and the second transmission line SL2 throughthe above via-hole 27.

The conductive land 32 is connected to the ground terminal GND shown inFIG. 2.

The conductive land 33 is connected to the capacitor electrode 23 usedfor the first capacitor C1 and the first transmission line SL1 by theabove via-hole 26.

The conductive land 35 is connected to the capacitor electrode 25 usedfor the fourth capacitor C4 and the second transmission line SL2.

The fifth capacitor C5, the first and second diodes D1 and D2, and theresistor R shown in FIG. 1 are composed of chips. As shown in both FIGS.2 and 3, the fifth capacitor C5 is mounted in such a manner that theconductive land 32 is linked to the conductive land 34. In addition, thefirst diode D1 is mounted in such a manner that the conductive land 31is linked to the conductive land 33. The second diode D2 is mounted insuch a manner that the conductive land 34 is linked to the conductiveland 35. The resistor R is mounted such that the conductive land 30 islinked to the conductive land 34.

As shown above, the high frequency switching component 1 has the circuitstructure shown in FIG. 1. In the high frequency switching component 1,as clearly shown in FIG. 2, on the surface of the multilayer circuitboard 2 are formed the transmission circuit terminal Tx, the receptioncircuit terminal Rx, the antenna terminal ANT, the ground terminal GND,the first diode D1, the second diode D2, the fifth capacitor C5, and theresistor R. In addition, at least a part of the signal line 3 connectingthe transmission circuit terminal Tx and the reception circuit terminalRx to the antenna terminal ANT is disposed inside the multilayer circuitboard 2. In addition, the first to third inductors L1 to L3 are providedby the line electrodes disposed inside the multilayer circuit board 2.

As described above, the present invention has been described byreferring to the disclosed embodiment. However, other variousmodifications are applicable without departing from the scope of theinvention.

For example, although the above embodiment has provided the first tothird inductors L1 to L3 which are formed by the line electrodesdisposed in the multilayer circuit board 2, at least one of the first tothird inductors L1 to L3 may instead be formed as a chip to be mountedon the surface of the multilayer circuit board 2. Also, chip capacitorscan be substituted for the first to fourth capacitors C1 to C4 disposedinside the multilayer circuit board 2. On the other hand, the fifthcapacitor C5 and/or the resistor R which are each formed as a chip mayinstead be disposed inside the multilayer circuit board 2.

Furthermore, in the above embodiment shown in the figures, each of thefirst to third inductors L1 to L3 is arranged corresponding to arespective one of the antenna terminal ANT, the transmission circuitterminal Tx, and the reception circuit terminal Rx. However, one or moreof the three inductors L1 to L3 may be omitted.

As described above, according to the above described structure andarrangement, since inductors used for eliminating noise are disposedbetween the signal line and the ground terminal in the high frequencyswitching component, noise components contained in high frequencysignals on the signal line can be carried to the ground terminal via theinductors. As a result, noise such as electrostatic surges can bereduced, and, for example, damage caused by the electrostatic surges tothe high frequency circuit can effectively be reduced.

Furthermore, since such inductors used for eliminating noise arearranged either on the surface of the multilayer circuit board or insidethe multilayer circuit board included in the high frequency switchingcomponent, the mounting of these inductors does not increase the areanecessary to mount the high frequency switching component. Furthermore,when compared with a case in which an additional noise-preventingcomponent is used, it is possible to decrease the area occupied on awiring board by a high frequency circuit including the high frequencyswitching component, and production cost can also be reduced.

In the present invention, miniaturization of the high frequencyswitching component can be achieved by using the line electrodes as theinductors for eliminating noise on lines disposed in the multilayercircuit board.

Furthermore, in the invention, since the inductor is disposed betweenthe ground terminal and the part at which the signal line is connectedto the antenna terminal, the inductor effectively works againstelectrostatic surges entering from an antenna. Therefore, damage causedby electrostatic surges to the high frequency switch and other circuitscan be reduced.

FIGS. 4 to 6 illustrate a high frequency switching component 101according to a second embodiment of the present invention.

First, referring to FIG. 4, a description will be given of the structureof a circuit disposed in the high frequency switching component 101.

The high frequency switching component 101 includes a transmissioncircuit terminal Tx0 for being connected to a transmission circuit, areception circuit terminal Rx0 for being connected to a receptioncircuit, an antenna terminal ANT0 for being connected to an antenna, anda ground terminal GND0. In addition, the high frequency switchingcomponent 101 includes a first control terminal T10 and a second controlterminal T20.

The transmission circuit terminal Tx0 is connected to the anode of afirst diode D10 via a first capacitor C10 and a second capacitor C20connected in series. The cathode of the first diode D1 0 is connected tothe antenna terminal ANT0 via a third capacitor C30 and a fourthcapacitor C40 connected in series.

The anode of the first diode D10 is connected to a ground terminal GND0,that is, the anode is grounded, via a series circuit constituted of afirst transmission line SL10 and a fifth capacitor C50. In addition, thefirst control terminal T10 is connected to the intermediate pointbetween the first transmission line SL10 and the fifth capacitor C50,and a control circuit connected to the first control terminal T10 can beused to control switching performed by the high frequency switchingcomponent 101.

The reception circuit terminal Rx0 is connected to the third capacitorC30 and the fourth capacitor C40 connected to the antenna terminal ANT0via a series circuit constituted of a second transmission line SL20 andthe sixth and seventh capacitors C60 and C70.

In addition, the anode of a second diode D20 is connected to theintermediate point between the second transmission line SL20 and thesixth capacitor C60. The cathode of the second diode D20 is connected toa ground terminal GND0 via an eighth capacitor C80, that is, the cathodethereof is grounded. The second control terminal T20 is connected to theintermediate point between the second diode D20 and the eighth capacitorC80 via a resistor R0. Another control circuit, connected to the secondcontrol terminal T20, can be used to control switching performed by thehigh frequency switching component 101.

In such a high frequency switching component 101, for connecting thetransmission circuit and the antenna to perform transmission, a positivevoltage is applied to the first control terminal T10 from the controlcircuit, which is not shown in the figure. With this applied voltage,both the first and second diodes D10 and D20 are switched on. In thissituation, since the DC voltage is blocked by the first to eighthcapacitors C10 to C80, the voltage applied to the first control terminalT10 is applied only to a circuit including the first and second diodesD10 and D20.

As described above, when the first and second diodes D10 and D20 areswitched on, a signal applied to the transmission circuit terminal Tx bythe transmission circuit is transmitted to the antenna via the antennaterminal ANT0. In addition, the signal from the transmission circuit isnot transmitted to the reception circuit terminal Rx0, since the secondtransmission line SL20 is placed in a resonant state by being groundedvia the second diode D20, and as a result, an impedance observed in thedirection of the reception circuit terminal Rx0 from a connecting pointA0 is extremely high.

Meanwhile, in the high frequency switching component 101, in order toconnect the reception circuit and the antenna to perform reception, novoltage is applied to the first control terminal T10, and a positivevoltage is applied to the second control terminal T20. With this appliedvoltage, both the first and second diodes D10 and D20 are switched off.As a result, a signal received from the antenna via the antenna terminalANT0 is transmitted to the reception circuit via the reception circuitterminal Rx0. Further, the received signal is not transmitted to thetransmission circuit via the transmission circuit terminal Tx0.

In this way, with the use of the high frequency switching component 101,the voltage applied to each of the first and second control terminalsT10 and T20 is controlled so as to switch to either a state in which thetransmission circuit is connected to the antenna, or a state in whichthe reception circuit is connected to the antenna.

In the high frequency switching component 101 described above, accordingto this embodiment, the first to sixth inductors L10 to L60 are disposedin such a manner that the LC filters LC10, LC20, and LC30 are formed byusing both the inductors L10 to L60 and the aforementioned first,second, third, fourth, sixth, and seventh capacitors C10, C20, C30, C40,C60, and C70 together. The LC filters LC10, LC20, and LC30 each form afourth-order high pass filter.

The first LC filter LC10 is formed by the first and second capacitorsC10 and C20, and the first and second inductors L10 and L20, which aredisposed between the signal line 103 passing through the capacitors C10and C20 and the ground terminal GND0.

The second LC filter LC20 is formed by the third and fourth capacitorsC30 and C40, and the third and fourth inductors L30 and L40, which aredisposed between the signal line 103 passing through the capacitors C30and C40 and the ground terminal GND0.

The third LC filter LC30 is formed by the sixth and seventh capacitorsC60 and C70, and the fifth and sixth inductors L50 and L60, which aredisposed between the signal line 103 passing through the capacitors C60and C70 and the ground terminal GND0.

As described above, since these LC filters LC10 to LC30 form high passfilters, these LC filters effectively serve to eliminate noisecomponents of frequencies lower than a signal frequency on the signalline 103, such as electrostatic surges.

Particularly, the second LC filter LC20 disposed near the antennaterminal ANT0 effectively allows an electrostatic surge which entersfrom the antenna to be attenuated, and serves to prevent theelectrostatic surge from entering either into the high frequencyswitching component 101 or into external circuits attached to theswitching component. As a result, the second LC filter LC20 preventsdamage both to the high frequency switching component 101 and toexternal circuits.

Furthermore, the LC filters LC10 to LC30 can be adapted to have theadditional function of performing matching adjustments between thetransmission circuit terminal Tx0, the reception circuit terminal Rx0,and the antenna terminal ANT0 in the high frequency switching component101.

FIG. 5 is a perspective view illustrating the appearance of the highfrequency switching component 101 comprising the circuit shown in FIG.4. FIG. 6 is an exploded perspective view of a multilayer circuit board102 disposed in the high frequency switching component 101 shown in FIG.5. In FIGS. 5 and 6, the same reference numerals are given to partsequivalent to those shown in FIG. 4 so that the linkages between FIGS.4, 5 and 6 can be easily understood.

The multilayer circuit board 102 disposed in the high frequencyswitching component 101, as shown in FIG. 6, is formed by laminating aplurality of insulation layers 104 to 113. The insulation layers 104 to113 are, for example, formed of dielectric materials.

Referring to FIG. 6, the description will start from the insulationlayer 104 at the bottom. On the first insulation layer 104, capacitorelectrodes 114, 115, and 116 for first, fourth, and seventh capacitorsC10, C40, and C70 are formed. The capacitor electrode 114 for the firstcapacitor C10 is connected to the transmission circuit terminal Tx0shown in FIG. 5. The capacitor electrode 115 for the fourth capacitorC40 is connected to the antenna terminal ANT0 shown in FIG. 5. Thecapacitor electrode 116 for the seventh capacitor C70 is connected tothe reception circuit terminal Rx0 shown in FIG. 5.

On a second insulation layer 105, other capacitor electrodes 117, 118,and 119 for the first, fourth, and seventh capacitors C10, C40, and C70are formed. These capacitor electrodes 117, 118, and 119 oppose thecapacitor electrodes 114, 115, and 116 described above through theinsulation layer 105.

On a third insulation layer 106, first, fourth, and sixth inductors L10,L40, and L60 are formed by line electrodes. The line electrodes forforming the first, fourth, and sixth inductors L10, L40, and L60 providemicrostrip line structures with a ground electrode 120, which will bedescribed below. In addition, the fourth and sixth inductors L40 and L60are provided by a series of the line electrodes.

On a fourth insulation layer 107 are formed capacitor electrodes 121,122, and 123 for second, third, and sixth capacitors C20, C30, and C60.

On a fifth insulation layer 108 are formed other capacitor electrodes124, 125, and 126 for the second, third, and sixth capacitors C20, C30,and C60. These capacitor electrodes 124, 125, and 126 oppose theaforementioned capacitor electrodes 121, 122, and 123 via the insulationlayer 108.

On a sixth insulation layer 109, second, third, and fifth inductors L20,L30, and L50 are formed by line electrodes. These line electrodes forforming the second, third, and fifth inductors L20, L30, and L50 providemicrostrip line structures with the ground electrode 120, which will bedescribed below. In addition, the third and fifth inductors L30 and L50are provided by a series of the line electrodes.

On almost the entire seventh insulation layer 110, the ground electrode120 is formed. The ground electrode 120 is connected to the groundterminal GND0 shown in FIG. 5.

On an eighth insulation layer 111 is formed a capacitor electrode 127for the fifth capacitor C50. The other capacitor electrode for the fifthcapacitor C50 is provided by the aforementioned ground electrode 120.

On a ninth insulation layer 112, line electrodes for first and secondtransmission lines SL10 and SL20 are formed. These first and secondtransmission lines SL10 and SL20 comprise microstrip line structuresformed by their line electrodes and the ground electrode 120.

On a tenth insulation layer 112 at the top are formed conductive lands128, 129, 130, 131, 132, 133, and 134. The conductive land 128 isconnected to the first control terminal T10 shown in FIG. 5. Theconductive land 129 is connected to the second control terminal T20shown in FIG. 5. The conductive land 131 is connected to the groundterminal GND0 shown in FIG. 5.

In addition, a description will be given of the connection between theinsulation layers 104 to 113. The conductive land 128, the firsttransmission line SL10, and the capacitor electrode 127 for the fifthcapacitor C50 are connected to one another through a via-hole 135.

The conductive land 130, the second transmission line SL20, the inductorL30, and the capacitor electrode 125 for the third capacitor C30 areconnected to one another through a via-hole 136.

The conductive land 132, the first transmission line SL10, the secondinductor L20, and the capacitor 124 for the second capacitor C20 areconnected to one another through a via-hole 137.

The conductive land 134, the second transmission line SL20, the fifthinductor L50, and the capacitor electrode 126 for the sixth capacitorC60 are connected to one another through a via-hole 138.

The first inductor L10 and the second inductor L20 are connected to theground electrode 120 through a via-hole 139. The third, fourth, fifth,and sixth inductors L30, L40, L50, and L60 are connected to the groundelectrode 120 through via-hole 140.

The capacitor electrode 121 for the second capacitor C20, the firstinductor L10, and the capacitor electrode 117 for the first capacitorC10 are connected to one another through a via-hole 141.

The capacitor electrode 122 for the third capacitor C30, the fourthinductor L40, and the capacitor electrode 118 for the fourth capacitorC40 are connected to one another through a via-hole 142.

The capacitor electrode 123 for the sixth capacitor C60, the sixthinductor L60, and the capacitor electrode 119 for the seventh capacitorC70 are connected to one another through a via-hole 143.

The eighth capacitor C80, the first and second diodes D10 and D20, andthe resistor R0 shown in FIG. 4 are formed of chips. As seen in FIGS. 5and 6, the eighth capacitor C90 is mounted such that the conductive land131 is linked to the conductive land 133. In addition, the first diodeD10 is mounted such that the conductive land 130 is linked to theconductive land 132. The second diode D20 is mounted such that theconductive land 133 is linked to the conductive land 134. The resistorR0 is mounted such that the conductive land 129 is linked to theconductive land 133.

In this way, the high frequency switching component 101 provides acircuit structure shown in FIG. 4. In the high frequency switchingcomponent 101, as clearly shown in FIG. 5, the transmission circuitterminal Tx0, the reception circuit terminal Rx0, the antenna terminalANT0, the ground terminal GND0, the first diode D10, the second diodeD20, the eighth capacitor C80, and the resistor R0 are disposed on thesurface of the multilayer circuit board 102. In addition, at least apart of the signal line 103 for connecting the transmission circuitterminal Tx0 and the reception circuit terminal Rx0 to the antennaterminal ANT0 is disposed inside the multilayer circuit board 102.Furthermore, the first to third LC filters LC10 to LC30 provided by theinductors L10 to L60 and the capacitors C10 to C40, C60 and C70,respectively, are disposed inside the multilayer circuit board 102.

Although the invention has been described by referring to the disclosedembodiment, various modifications can be applied within the scope of thepresent invention.

For example, in the embodiment shown in the figures, the first to thirdLC filters LC10 to LC30 are provided by the inductors L10 to L60, andthe capacitors C10 to C40, C60 and C70. However, at least one of the LCfilters LC10 to LC30 may be formed by a chip filter component.Alternatively, at least one of the inductors and the capacitors formingat least one of the LC filters LC10 to LC30 may be formed as a chip tobe mounted on the surface of the multilayer circuit board 102. The sameis true of the fifth capacitor C50 disposed inside the multilayercircuit board 102. On the other hand, the resistor R0 formed as a chipcomponent may instead be disposed inside the multilayer circuit board102.

Furthermore, in the embodiment shown in the figures, the first to thirdLC filters LC10 to LC30 are connected respectively to the antennaterminal ANT0, the transmission circuit terminal Tx0, and the receptioncircuit terminal Rx0. However, one or more of the three LC filters LC10to LC30 may be omitted.

In addition, in the embodiment shown in the figures, the LC filters LC10to LC30 form fourth-order high pass filters. However, regardless of whatorder filter they are, according to the frequency of the noise to beeliminated, low pass filters or band pass filters may be used instead.

As described above, according to the above described structure andarrangement, since LC filters for eliminating noise are connected to thesignal line in the high frequency switching component, a noise componentcontained in a high frequency signal on the signal line can beeliminated via the LC filters. As a result, for example, noise such asan electrostatic surge can be reduced, and damage caused by theelectrostatic surge to the high frequency circuit can be effectivelyreduced. In order to enhance such a noise-eliminating effect, it is onlynecessary to increase the number of stages in the LC filter.

In addition, since the noise-eliminating LC filters are disposed insideor on the surface of the multilayer circuit board arranged in the highfrequency switching component, they do not increase the area required tomount the high frequency switching component. Furthermore, when comparedwith a case in which a separate noise-preventing component is added, thearea of the wiring board required for mounting a high frequency circuitincluding the high frequency switching component can be made smaller,and the cost of production can also be reduced.

In addition, when the inductor is inserted between the signal line andthe ground to prevent noise, the smaller the inductance value, thegreater the noise-eliminating effect. However, in contrast, since theinsertion loss becomes greater, negative effects are caused on thecharacteristics of the high frequency circuit. However, as in the caseof the present invention, with the use of the LC filters, even thoughthe inductance value is smaller, it is easy to obtain matching. As aresult, with no problem to decrease the inductance value, thenoise-eliminating effects can be enhanced.

Furthermore, since the LC filters also can function as matchingadjustment circuits, matching adjustment circuits are unnecessary or canbe simplified. With this arrangement, reduction of the mounting area andthe cost can be achieved.

In this invention, since the LC filters for eliminating a noise aredisposed inside the multilayer circuit board, the high frequencyswitching component can be miniaturized.

Additionally, in the present invention, since the LC filter is insertedat the part at which the signal line is connected to the antennaterminal, the LC filter effectively serves against an electrostaticsurge entering from the antenna. As a result, damage caused by such anelectrostatic surge to the high frequency switch can be reduced, anddamage to external circuits attached thereto.

While the invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that the foregoing and other changes in formand details may be made therein without departing from the spirit of theinvention.

What is claimed is:
 1. A high frequency switching component for beingconnected to a transmission circuit, a reception circuit, and an antennato be used for switching either to a state in which the transmissioncircuit is connected to the antenna, or a state in which the receptioncircuit is connected to the antenna, the high frequency switchingcomponent comprising: a multilayer circuit board, on which there isformed a circuit including: a transmission circuit terminal to beconnected to the transmission circuit; a reception circuit terminal tobe connected to the reception circuit; an antenna terminal to beconnected to the antenna; a ground terminal; a first diode connected tothe transmission circuit terminal and to the antenna terminal; a seconddiode connected to the reception circuit terminal and to the groundterminal; a signal line for connecting the transmission circuitterminal, the reception circuit terminal, and the antenna terminal viathe first diode; and an inductor disposed between the signal line andthe ground terminal which is effective to eliminate an electrostaticsurge occurring on the signal line, the inductor being provided by aline electrode disposed inside the multilayer circuit board; wherein thetransmission circuit terminal, the reception circuit terminal, theantenna terminal, the ground terminal, the first diode, and the seconddiode are disposed on a surface of the multilayer circuit board; atleast a part of the signal line is disposed inside the multilayercircuit board; and the inductor is opposed to a around electrodeprovided adjacent to the bottom surface of the multilayer circuit board.2. The high frequency switching component according to claim 1, whereinsaid inductor eliminates an electrostatic surge entering the signal linefrom the antenna.
 3. The high frequency switching component according toclaim 1, wherein the inductor is disposed between the ground terminaland a part of the signal line at which the signal line is connected tothe antenna terminal.
 4. The high frequency switching componentaccording to claim 3, wherein said inductor eliminates an electrostaticsurge entering the signal line from the antenna.
 5. The high frequencyswitching component according to claim 3, wherein said inductor isconnected directly to the signal line and to the ground terminal.
 6. Thehigh frequency switching component according to claim 1, wherein theinductor is disposed between the ground terminal and a part of thesignal line at which the signal line is connected to the antennaterminal.
 7. The high frequency switching component according to claim6, wherein said inductor eliminates an electrostatic surge entering thesignal line from the antenna.
 8. The high frequency switching componentaccording to claim 6, wherein said inductor is connected directly to thesignal line and to the ground terminal.
 9. The high frequency switchingcomponent according to claim 1, wherein said inductor is connecteddirectly to the signal line and to the ground terminal.
 10. A highfrequency switching component for being connected to a transmissioncircuit, a reception circuit, and an antenna to be used for switching toeither a state in which the transmission circuit is connected to theantenna, or a state in which the reception circuit is connected to theantenna, comprising: a multilayer circuit board, on which there isformed a circuit including: a transmission circuit terminal to beconnected to the transmission circuit; a reception circuit terminal tobe connected to the reception circuit; an antenna terminal to beconnected to be the antenna; a ground terminal; a first diode isconnected to the transmission circuit terminal and to the antennaterminal; a second diode is connected to the reception circuit terminaland to the ground terminal; a signal line for connecting thetransmission circuit terminal, the reception circuit terminal, and theantenna terminal via the first diode; and an LC filter connected to thesignal line which is effective to eliminate an electrostatic surgeoccurring on the signal line, the LC filter being disposed inside themultilayer circuit board; wherein the transmission circuit terminal, thereception circuit terminal, the antenna terminal, the ground terminal,the first diode, and the second diode are disposed on a surface of themultilayer circuit board; at least a part of the signal line beingdisposed inside the multilayer circuit board; and the LC filter isprovided between the bottom surface of the multilayer circuit board anda ground electrode disposed inside the multilayer circuit board.
 11. Thehigh frequency switching component according to claim 10, wherein saidLC filter eliminates an electrostatic surge having a frequency lowerthan a signal on the signal line.
 12. The high frequency switchingcomponent according to claim 10, wherein the LC filter is connected to apart of the signal line at which the signal line is connected to theantenna terminal.
 13. The high frequency switching component accordingto claim 12, wherein said LC filter eliminates an electrostatic surgeentering the signal line from the antenna.
 14. The high frequencyswitching component according to claim 12, wherein the LC filter isconnected directly to the signal line and to the ground terminal. 15.The high frequency switching component according to claim 10, whereinthe LC filter is connected directly to the signal line and the groundterminal.
 16. The high frequency switching component according to claim10, wherein said LC filter eliminates an electrostatic surge enteringthe signal line from the antenna.
 17. The high frequency switchingcomponent according to claim 10, wherein the LC filter is connected to apart of the signal line at which the signal line is connected to theantenna terminal.
 18. The high frequency switching component accordingto claim 17, wherein said LC filter eliminates an electrostatic surgeentering the signal line from the antenna.
 19. The high frequencyswitching component according to claim 17, wherein the LC filter isconnected directly to the signal line and to the ground terminal.